Furnace with flue gas condensate neutralizer

ABSTRACT

A high efficiency domestic furnace incorporates means for separating and neutralizing flue gas condensate. Acidic condensate from the flue gas products of combustion is neutralized by contact with neutralizing material in a housing through which the condensate is flowed. The use of the neutralizer in connection with a high efficiency domestic furnace permits discharge of the condensate directly to the household drain. The neutralizer is arranged to be self-flushing and defines a serpentine, series flow path and is arranged to discharge the neutralized condensate as a result of the entry of additional acidic condensate at its inlet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to domestic furnaces, and in particular to afurnace having means for effectively separating and neutralizing acidiccondensate from the flue gas and suitably discharging the condensate toa household drain.

2. Prior Art

In U.S. Pat. No. 4,164,210 of George T. Hollowell, a domestic-typefurnace is shown to have a secondary heat exchanger providing a highefficiency wherein the flue gases are discharged at a relatively lowtemperature whereby a portion thereof may condense. To remove anyresulting condensate, a drain is provided at the bottom of the secondaryheat exchanger.

A problem arises in a furnace system such as taught by the Hollowellpatent in that the products of combustion of conventional hydrocarbonfurnace fuels include acidic products. Natural gas, for example,frequently contains some amount of sulfur which, when burned with thegas, produces sulfur dioxide or sulfur trioxide in addition to thenormal combustion products of carbon dioxide and water vapor. Whencondensed, these combustion products produce a weak sulfuric acidsolution. The dumping of such acidic condensate directly into aconventional household drain may not be advisable in all cases. Thepresent invention comprehends providing an improved neutralizing meansfor neutralizing such acidic condensate, permitting satisfactorydischarge of the condensate into the conventional household drain.

A number of prior art patents disclose commercial means for thescrubbing of gas. Illustratively, Roger Kent, in U.S. Pat. No.3,683,593, shows a gas scrubber having a wet filter bed with layers ofstacked filter elements. Charles S. Viers, in U.S. Pat. No. 3,735,567,shows a gas scrubber in the form of a muffler provided with a filtercontaining gas-cleaning water. The exhaust gas pressure is utilized tovaporize and circulate the gas-water mixture over the filtering materialso as to improve the gas washing and filtering action and preventclogging.

Henry Burbach, in U.S. Pat. No. 3,726,239, discloses a wet scrubberemploying a bed of marble for producing a mixture of the wash water andflue gas. The Viers U.S. Pat. No. 3,735,567 discussed above utilizeslime rock for neutralizing acid-forming components of the exhaust gasesin the muffler structure.

In U.S. Pat. No. 3,751,231, Albert Niedzielski utilizes a porous acidion exchange resin, such as a resin formed of sulfonated copolymer ofstyrene and divinylbenzene for removing amines from a steam distributionsystem.

Another furnace structure which discharges condensate from the fluegases directly to the building drain is shown in U.S. Pat. No. 3,944,136of Edwin C. Huie.

John D. Hilliard, in U.S. Pat. No. 1,620,155, shows an attachment foroil insulated switches for preventing the throwing out of oil as uponopening of a high-power circuit under oil. Hilliard teaches the use of ahousing enclosing a mass of gravel or artificially prepared spheroidalbodies in a serpentine flow path for separating much of the oil vaporand atomized oil from the discharging gases while, at the same time,cooling the gases to a low temperature for safe discharge to theexternal atmosphere.

SUMMARY OF THE INVENTION

The present invention comprehends an improved domestic furnace systemwherein condensate which would otherwise enter or form in the dischargeflue as a result of the relatively high efficiency heat transfereffected in the furnace is substantially removed ahead of the flue andneutralized. As indicated above, the products of combustion dischargedthrough such a flue may include acidic components which, when condensedout, form an acid condensate which may adversely affect the metal orother materials of the conventional domestic drain. The presentinvention comprehends a means for separating and neutralizing asubstantial portion of the acidic cndensate so as to permit safe dumpingof the condensate to the domstic drain.

The invention further comprehends the provision of such a neutralizingmeans which is effectively self-flushing so as to effect an automaticremoval of sediment therefrom as an incident of the normal cyclicoperation of the furnace itself.

More spcifically, the invention comprehends the provision of aneutralizer wherein suitable neutralizing material is provided in a flowpath arranged to provide sufficient contact between the condensate andneutralizing material for proper neutralizing action. The structure isarranged so that a small amount of the neutralized condensate isdischarged as a result of a corresponding amount of acidic condensatebeing delivered to the inlet of the neutralizer.

In the illustrated embodiment, the furnace is provided with combustionair moving means providing a negative pressure in the combustion chamberand in the condensate separating means which, in turn, is connected tothe neutralizer through a suitable conduit. Thus, during the fuelburning operation, a negative pressure is applied to the neutralizer,urging the collected condensate therein back upstream toward thecondensate separator. Following termination of the fuel burningoperation, operation of the air moving means is also terminated so thatthe negative pressure is correspondingly removed from the neutralizer.This allows the condensate to run downstream under the influence ofgravity, causing a flow through the neutralizer and thereby effecting adesired flushing action therethrough. The flushing action results fromthe fact that the flow through the neutralizer under the aboveconditions is more forceful than the gradual flow that takes placeduring continuous operation of the air moving means.

The normal flow of the condensate through the condensate separator intothe neutralizer may be effected by gravity. As a result of theneutralizer being filled with the condensate being treated by theneutralizing material therein, additional condensate delivered from theseparator causes previously neutralized condensate to be urged outwardlyfrom the neutralizer and discharged through a suitable connection to thedomestic drain.

The present invention also comprehends the provision of means forcollecting condensate that may form in the flue pipe and returning thiscondensate to the neutralizer. In the illustrated embodiment, this isaccomplished by providing a condensate collecting means at the base of avertically disposed flue pipe and by providing conduit means connectingthe collecting means with the inlet side of the condensate separator.

Thus, the present invention comprehends a domestic furnace havingcondensate treatment means which removes and neutralizes a substantialamount of acidic moisture from the flue gas before the gas passesthrough an air moving means and enters the furnace flue, therebyreducing the amount of acidic condensate that would otherwise form inthese components. The removed condensate is neutralized by means of aninexpensive, self-contained apparatus particularly adapted for use in adomestic furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from thefollowing description taken in connection with the accompanying drawingswherein:

FIG. 1 is a front view of a domestic furnace provided with a flue gascondensate treatment means embodying the invention;

FIG. 2 is a fragmentary enlarged perspective view illustrating thecondensate neutralizer in greater detail;

FIG. 3 is an enlarged fragmentary elevation illustrating the condensateseparator in greater detail; and

FIG. 4 is a vertical section taken substantially along the line 4--4 ofFIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

In the exemplary embodiment of the invention as disclosed in thedrawing, a domestic furnace generally designated 10 is shown to comprisea high efficiency furnace having a primary heat exchanger generallydesignated 11 and a secondary heat exchanger (not shown). The furnace isprovided with a suitable cabinet 12. Products of combustion aredischarged from the furnace through a flue 13. An air moving means inthe form of a blower 14 is connected to the interconnecting duct 15leading from the secondary heat exchanger for forcibly discharging theproducts of combustion resulting from the burning of the fuel as byburner 16.

In the illustrated embodiment, furnace 10 comprises a forced air furnacehaving a heated air blower 17 mounted in a lower portion of cabinet 12.

As shown in FIG. 1, the duct 15 may be provided with a condensateseparator, or collector, 18. As illustrated in FIGS. 3 and 4, theseparator may define an enlarged cylindrical housing 19 having adepending baffle 22 extending partially downwardly therethrough causingthe flue gases to pass circuitously under the baffle from the inlet 20to the outlet 21 thereof.

In a high efficiency furnace, such as the present furnace employing asecondary heat exchanger or a furnace having a primary heat exchangerdesigned to remove a sufficient amount of heat from the combustiongases, the combustion products exiting from the heat exchanger to theflue will contain condensate and some water vapor. The presence of thecondensate is due to the relatively low temperature of the gases as theyexit from the heat exchanger. It is desirable to remove such condensateprior to the delivery of the flue gas to the air moving means 14 and theflue 13 because the condensate will normally include acidic components.

As shown in FIGS. 1, 3 and 4, the separator is provided with a dependingcondensate outlet 23 for draining the lower portion of the housing 19 inwhich the condensate collects. As shown in FIG. 1, the outlet 23 isconnected through a flexible conduit 24 to a neutralizer generallydesignated 25 which, illustratively, may be carried on the sidewall ofcabinet 12. Neutralizer 25 effectively neutralizes acidic components ofthe condensate before discharging the neutralized condensate through adischarge line 26 to the conventional domestic drain 27.

Neutralizer 25 is shown in greater detail in FIG. 2. As illustratedtherein, the neutralizer includes an outer housing 28 which may comprisea parallelepiped housing having a top wall 29 provided with an inletconnector 30 to which the lower end of conduit 24 is connected. Anoutlet connector 31 is further provided in the top wall 29 forconnection thereto of the drain line 26.

The interior of housing 28 may be divided by a plurality of baffles 32to define a serpentine path 33 through which condensate from separator18 must flow in passing from inlet 30 to outlet 31. Suitableneutralizing material 34 is provided within the housing for neutralizingthe acidic components of the condensate within the neutralizer.Illustratively, the neutralizing material may comprise crushed limestoneor calcium carbonate, etc.

As shown, the housing 28 may be mounted to the sidewall of cabinet 12 bysuitable bracket 35. To facilitate neutralization, the neutralizer maybe agitated or vibrated as by mechanical interconnection to the blower17. In the illustrated embodiment, the mechanical interconnection iseffected by a bracket 36 having one leg connected to the blower and oneleg connected to the housing 28. Alternatively, the neutralizer may bemounted to the blower rather than to the sidewall of cabinet 12.

The furnace may include suitable controls 37 for controlling theautomatic heating operation. More specifically, the furnace iscontrolled so as to cause operation of the blower 14 concurrently withthe operation of the burner 16.

After a period of time of operation of the furnace, a sufficient amountof condensate is transferred from the separator 18 to the neutralizer soas to completely fill the neutralizer. Thus, additional condensatedelivered from the separator under this condition will cause acorresponding amount of the neutralized condensate to pass outwardlythrough connector 31 and conduit 26 to drain 27. Such transfer isautomatically effected by gravity without the need for valves, pumps,etc.

As can be seen in FIG. 1, when blower 14 is operated to discharge theproducts of combustion upwardly through the flue 13, a negative pressureis created within the separator 18 in drawing the products of combustiontherethrough. At the same time, this negative pressure is present in thecondensate outlet 23, conduit 24, and inlet connector 30 on theneutralizer. When the furnace cycles off so as to discontinue burningoperation of the fuel in burner 16 and the operation of blower 14, thenegative pressure on the inlet portion of the neutralizer is eliminated,allowing liquid in the neutralizer to seek the normal level therein.When the negative pressure is applied, however, it tends to draw thecondensate collected in the neutralizer 25 back upwardly through theinlet connector 30 and into conduit 24. The neutralizer is constructedand arranged to make advantageous use of this pressure change, asdescribed below.

Due to the action of the acidic condensate on the neutralizing material,a sediment builds up within the neutralizer over a period of operation,and it is desirable to prevent this sediment from building up to a pointwhere operation of the neutralizer is inhibited due to clogging orcaking of the neutralizing material. The gradual flow of condensateduring operation of the burner 16 and blower 14 may not be sufficientlyforceful to flush an appreciable amount of sediment through theneutralizer. A more forceful flushing action can be obtained, however,by locating the neutralizer such that the condensate drawn back upstreamtoward the separator under negative pressure conditions is periodicallycaused to flow rapidly back into the neutralizer under the influence ofgravity upon termination of the negative pressure. This forceful returnflow of the condensate causes a comparatively rapid discharge ofcondensate from the neutralizer outlet 31, and this discharge carrieswith it a portion of the accumulated sediment.

To create this self flushing action, the neutralizer inlet 30 should belocated sufficiently below the separator condensate outlet 23 andconduit 24 should be sized so as to create a head or reservoir above theneutralizer into which an amount of condensate can be drawn duringnegative pressure conditions. It is necessary that the neutralizer beconstructed so as to prevent air from being drawn therethrough from itsoutlet 31 to its inlet 30 during such conditions, since such an airbypass would prevent condensate from being drawn upstream into theconduit 24. The serpentine flow path created by baffles 32 prevents sucha bypass and ensures a first in--first out, or serial, flow that isdesirable for best neutralizing action.

It has been found that a self flushing action does not necessarily takeplace after each cycle of the blower 14, but that the head of condensateformed or drawn back upstream into conduit 24 during negative pressureconditions gradually increases with each cycle of the furnace until therapid, forceful flushing occurs. By way of example for a neutralizerconstructed as shown in FIG. 2 and containing approximately four poundsof marble stone as the neutralizing agent, a condensate head ofapproximately four inches will build up under negative pressure inconduit 24 after about 25 cycles of the furnace. It is at this pointthat a rapid, and hence, forceful, flushing action takes place uponremoval of the negative pressure in conduit 24. Prior to this forcefulflushing action, the condensate drawn into conduit 24 above theneutralizer flows slowly back into the neutralizer at the end of eachcycle, without creating a forceful flushing action. This gradualback-and-forth flow of condensate through the neutralizer prior to therapid flushing action is also believed to enhance the neutralizingaction because it provides a mild stirring or washing effect.

Thus, the neutralizer utilizes variable pressure conditions existingwithin the furnace structure to effect the desired self-flushing andself-washing action. As a result, facilitated neutralizing action isprovided, permitting the condensate from the combustion products to bedrained directly to the conventional household drain in a novel andsimple manner. The self-flushing and self-washing action provides highefficiency in the utilization of the neutralizing material within theneutralizer so that a long operating life between recharging of theneutralizer is obtained. Again, by way of example, a natural gas furnacehaving a heating capacity of 80,000 BTU/hour produced condensate at arate of approximately six pounds per hour of operation, and the rate ofconsumption of neutralizing material was measured to be 0.81 pounds per1800 hours of operation for the neutralizer structure shown anddescribed herein.

Proper operation of the separator 18 notwithstanding, some condensatemay accumulate in the flue 13 as the flue gases are passed therethrough.The present invention provides means for preventing this condensate fromrunning down the flue 13 and into the blower 14 during periods when thefurnace has cycled off. Referring to FIGS. 2 and 3, a manifold orcollecting means 38 is provided at the outlet of the blower 14. Theblower 14 discharges horizontally into the collecting means 38 and fluepipe 13 extends vertically therefrom. A flexible conduit 39 connects thelower portion of collecting means to a second inlet 20a on separator 18.Thus, any condensate running down the flue 13 will collect in thecollecting means 38 and be conducted to the separator 18 instead ofentering blower 14.

The neutralizing means of the present invention is particularly usefulin connection with high efficiency furnaces, such as those having athermal efficiency of 90% or more, in which a considerable amount ofcondensate will form due to the relatively low temperature of theproducts of combustion as they are discharged from the furnace.

The neutralizer is relatively small and simple so as to be economical ofconstruction and readily mounted within the furnace structure. Theneutralizing material is readily obtainable and is similarly low cost.

The foregoing disclosure of specific embodiments is illustrative of thebroad inventive concepts comprehended by the invention.

I claim:
 1. In a domestic furnace having means for burning fuelresultingly producing gaseous products of combustion and means forexhausting the gaseous products of combustion wherein acidic condensatemay result from cooling of gaseous acid-forming components in thegaseous combustion products, the improvement comprising:means forneutralizing the acidic condensate; means for conducting acidiccondensate from the exhausting means to the neutralizing means; anddischarging means for discharging the neutralized condensate from theneutralizing means.
 2. The domestic furnace structure of claim 1 whereinthe neutralizing means includes a housing and means in said housing forneutralizing the condensate therein, and said discharging meanscomprises means for conducting the neutralized condensate from thehousing.
 3. The domestic furnace structure of claim 1 wherein theneutralizing means includes a housing means in said housing defining avertically serpentine path through which the condensate flows, and meanswithin said serpentine path for neutralizing the condensate therein, andsaid discharging means comprises means for conducting the neutralizedcondensate from the housing.
 4. The domestic furnace structure of claim1 wherein the neutralizing means includes a housing having an inlet andan outlet, the conducting means comprising means for conducting theacidic condensate by gravity downwardly from the exhausting means intosaid housing inlet, and means in said housing for neutralizing theacidic condensate therein, and said discharging means comprises meansfor conducting the neutralized condensate from the housing outlet.
 5. Ina domestic furnace having means for intermittently burning fuelresultingly producing gaseous products of combustion, and means forexhausting the gaseous products of combustion wherein acidic condensatemay result from cooling of gaseous acid-forming components in thegaseous acid-forming components in the gaseous combustion products, theimprovement comprising:means for neutralizing the acidic condensate,said neutralizing means being connected to receive condensate from saidexhausting means and responsive to the intermittent operation of thefurnace for periodically flushing a quantity of condensate therethrough.6. The domestic furnace structure of claim 5 wherein said exhaustingmeans includes an air moving means operated concurrently with said fuelburning means to apply a negative pressure to said products ofcombustion and to said neutralizing means, said condensate flushingbeing effected as a result of the cyclic operation of said air movingmeans.
 7. The domestic furnace structure of claim 5 wherein theneutralizing means defines a housing, means for conducting the acidiccondensate into said housing and means in said housing for neutralizingthe acidic condensate therein, said exhausting means including an airmoving means operated concurrently with said fuel burning means to applya negative pressure to said housing and thereby effect an intermittentmovement of the condensate in the housing, the housing being filled withcondensate under normal operating conditions of the furnace apparatuswhereby additional acidic condensate delivered to the housing displacesa corresponding quantity of neutralized condensate therefrom.
 8. In adomestic furnace having a fuel burner, a heat exchanger for receivinggaseous products of combustion from said burner, and exhaust meansincluding an exhaust blower for creating a negative pressure within saidheat exchanger and duct means connecting said heat exchanger with saidblower, the improvement comprising:separating means connected in saidexhaust duct ahead of said blower for separating acidic condensate whichmay result from cooling of gaseous acid-forming components in thegaseous products of combustion, said separator including an outlet fordischarging said condensate; and neutralizing means for neutralizingacidic condensate contained therein, said neutralizing means having aninlet and means connecting said inlet with said separating means outletfor receiving a gravitationally induced flow of the acidic condensatetherefrom, said separating means, blower, and neutralizing means beingarranged such that operation of said blower creates a negative pressureat the inlet of said neutralizer.
 9. The domestic furnace structure ofclaim 8 wherein said exhaust means include a flue located downstream ofsaid blower and said furnace further includes means for conductingcondensate from said flue to said neutralizer.
 10. The domestic furnacestructure of claim 9, wherein said blower discharges horizontally intosaid flue, said flue includes condensate collecting means, and saidmeans for conducting condensate comprises a conduit connecting saidcondensate collecting means with said separating means.